Grinding apparatus



April 2, 1957 R. w. SUNDBERG GRINDING APPARATUS 4 5 9 l 8 h C r a M d e l i F INVENTOR RA) W SUNDBERG -w mnH-w Br V; 6.?(11,

PATENT AGENT GRINDING APPARATUS Ray W. Sundberg, San Jose, Calif.

Application March 8, 1954, Serial No. 414,690 3 Claims. (Cl. 51-111) to render the known apparatus unsatisfactory in many respects.

Accordingly, it is an object of the present invention to provide a grinding apparatus which will enable the controlled grinding of a rock into a desired conformation, however irregular the rock might be in its natural state.

Another object of the invention is to provide a grinding apparatus which can be utilized to grind rocks into any of a great number of curved shapes.

A further object of the invention is to provide a grinding apparatus which can be operated with optimum eifect throughout the full cycle from the inception, when the rock is quite irregular, to the later stages, when the rock is relatively smooth and regular in shape.

It is another object to provide a grinding apparatus which reduces the danger of injury of the operator to the very minimum.

Additionally, an object of the invention is to provide a grinding apparatus constituting a simple, compact and relatively inexpensive unit and which is substantially free from the damaging effects of the abrasive material.

These and other objects as well as the advantages accruing from the present invention will become apparent from the following description taken in conjunction with the accompanying drawing wherein:

Figure 1 is a side elevation of a grinding apparatus embodying the present invention in a preferred form,

Figure 2 is a top plan view of the grinding apparatus shown in Figure 1,

Figure 3 is a section taken along line 33 in Figure 2 showing details of construction of the grinding cups, and

Figure 4 is a sectional view similar to Figure 3 but with the cups arranged to enable a final grinding or polishing operation on the rock.

As shown in the drawing, the grinding apparatus includes a pair of grinding elements 10, 10 adapted to engage the opposite sides of a rock, generally indicated at R, so as to support the same and also to effect grinding of the rock upon rotation in a manner to be described hereinafter. The grinding elements 10, 10' are of like construction and are mounted for rotation in accordance with the present invention on separate drive units 11, 11 which also are similar so that only one grinding element and one drive unit will be described, and the corresponding portions of the other will be indicated by the same numerals with an added prime notation.

The grinding element 10 is cup-shaped, being formed nited States Patent by a short, cylindrical metal tube 12 to one end of which a centrally-apertured disc 13 is secured by welding. The aperture in the disc 13 is threaded so that the grinding element 10 can be screwed onto the threaded end of a shaft 14 and be caused to lodge securely thereon through frictional engagement with a collar 15 which is welded or otherwise rigidly fastened to the shaft 14 for rotation, therewith.

The described shaft emerges from a conventional gearreducer 16 which is mounted on one side of a driving motor 17 supported on a base member 18. This base member 18 is adapted in accordance with the invention to support the motor 17 so that the axis of the described shaft 14 and cup-shaped driving element extends at a slight upward angle from the horizontal and can be adjusted to permit limited variance of this angularityv To this end, the base member 18 of the right drive unit 11, which is formed of a flat metal top and triangular sides is secured to a plate 19 that is bolted at its outermost end to a rectangular supporting frame 20 in a manner such that limited vertical pivoting of the drive unit 11 is permitted. The pivotal position is varied by means of a pair of adjustment bolts, 21, connecting the other innermost end of the plate 19 to the frame 20, and such position is maintained through the use of suitable lock nuts, indicated at 22, in a well-known fashion. A pointer 23 on the drive unit 11 is arranged adjacent a scale 24 on the supporting frame 20 to indicate the amount of angularity, which preferably is between 6 and 10.

The supporting frame 20 is part of a carriage unit which also includes angle irons 25, 26 at its ends which are suitably apertured to slidingly encompass transversely spaced and parallel metal rods 27, 28 mounted in brackets 29 on a platform 30 of wood or metal. The other or left-hand grinding element 10' and associated drive unit 11 is mounted directly on this platform with provision made for vertical pivotal adjustment in the manner described with respect to the right-hand unit but with no provision for sliding movement. Thus, it will be seen that the left-hand unit 11' is maintained in a set position on the platform 30 while the right-hand unit 11 may be shifted on the rods 27, 28 as indicated by the phantom line showing in Figure 1 to vary the spacing between the grinding elements 10, 10 supported respectively thereby. A spring 31 urges the right-hand unit 11 toward the other unit, such spring 31 being connected between the carriage unit and the end of a chain 32 which passes under the left-hand unit 11 and can be secured at various points to a protuberance 33 on the platform to vary the tension on the spring.

Electrical energy is not supplied directly to the motors 17, 17' but rather, in accordance with the present invention, separate switches 35, 35' and control rheostats 36, 36' are electrically connected to the motors so that distinct and continuously variable control is provided for each motor and thus for each of the cup-shaped grinding elements 10, It). The rotation of the motors 17, 17' is such that the respective grinding elements 10, 10 rotate in opposite directions as is required in this type of grinding operation, and the speed of rotation of the elements can be varied between 50 and 300 revolutions per minute by use of the control rheostats 36, 36.

When a given rock or similar article is to be ground, grinding elements 10, 10' somewhat smaller in diameter than the rock are secured on the shafts 1.4, 14 respectively and the angularity adjusted as desired. In most instances, an angle of 7 has been found optimum in that support is provided for the rock but it is not able to jump upwardly from between the grinding elements. The right-hand element 10 and the associated drive unit 11 are then pulled to the right, as indicated by the l, and-the rock is then held-against the left-.handgrind:v

ing element 10' while the right-hand unit is permitted to return under action of thespring 31 towards the left so that 'the grinding element 10' thereon comes against the roughsurfaCeof the' unground rock.

Abrasive material is supplied in a liquid mixture commonly referred-to as mud to the surface of the rock and the switches 35, 35 are thrown to start rotation of the grinding elements 10,10. The abrading or grinding action takes place as'the mud is held against the rock by the lip of the cup-shaped grinding elements, the desired force being obtained -by adjustment of the described spr'ing Sl. The rheostats are set at a slow speed, for examp'le,'l00 R. P. M., when grinding of an irregular rock is first started to prevent overmuch vibration. At later stages of grinding; when the rock has become more smooth, the speed can be increased until the maximum of 300 R. P. M. is reached during the final stages. To complete the operation, leathers 3'7, 37' can be held over the open ends of the grinding elements 111, 10 by suitable clamps '38, 38 as shown in Figure 4, and rouge employed to give a final polish to the surface.

Usually the grinding elements it), 10 can be run at approximately the same speeds with the opposite rotation thereof and the irregularities on the rock surface serving to maintain a continuous turning of the rock in all directions so that an even grinding will occur. However, in some instances, such is not the case and a variation in the speed of one grinding element, as provided 1 by the apparatus of the invention, enables the grinding to proceed evenly. Additionally, variation of the speed of one grinding element enables the production of a polished rock in shapes other than the exact sphere. If one element is run faster than the other and the rock is manually restrained, an egg-shape will result, and other variations fronrthe spherical shape are obviously permitted through such techniques.

During the grinding operation, and particularly when the gri-ndi-ng elements are revolving quite fast a certain amount of the mud will be thrown from the rock by the centrifugal force. However, it will be noted that the rock is in a position between the motors 17, 17' and other'parts of thedrive units 11, '11 so that the mud will seldom be thrown thereon. However, it will additionally be noted that the motors 17, 17 and gear reducers 16, 16 are completely covered to provide protection against whatever stray mud might occasionally be thrown thereagainst. Such covered construction for all of the rapidly-rotating parts of the grinding apparatus additionally functions as a safety measure which is so important in a device such as this where the operator necessarily must use his hands.

Various alterations and modifications of the described structure. can-.obviousl.y.b.e made without departing from. the spirit of the invention. Accordingly, the description is to be considered as purely exemplary and the scope of the invention is indicated by the appended claims.

I claim:

1. Grinding apparatus for rocks or the like comprising a pair of cup-shaped grinding elements, means supporting said elements in facing relationship for rotation about axes intersecting atan angle lying in a vertical plane whereby a rock can be supportingly engaged there between, and means for adjusting the angle of intersection of said axes.

2. In a grinding apparatus for rock or the like having a pair of cup-shaped grinding elements, means supporting said elements in facing relationship for individual rotation about axes intersecting at an angle lying in a vertical plane whereby a rock can be supportingly engaged therebetween, and means mounting said supporting means for edjustment'to vary thetangle of intersection of said axes.

3. Apparatus for grinding rocks to spherical or other curved conformations comprising a pair of cup-shaped grinding elements, independent drive means including a speed reducer and .a motorrrigidly supporting each of said grinding elements for rotation, means including a rheostat forcontroliing the speed of each of said motors in a continuouslywariable manner, a pair of base members supporting said drive means for said grinding elements whereby the latter are disposed in facing relationship, each .of said base members being mounted for limited pivotal movement whereby the rotative axis of each grinding element can be pivoted in a vertical plane, means supporting said base members for relative movement :whereby the spacing between said grinding elementscan be varied, and means urging said base members relatively toward one another whereby a rock disposed'between said cup-shaped grinding elements will be resiliently engaged and supported therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,042,794 Irwin Oct. 29, 1912 1,072,868 Monfils Sept. 9, 1913 1,550,712 Smith Aug. 25, 1925 1,767,091 Millsap June 24, 1930 1,994,975 Williams Mar. 19, 1935 2,008,276 Giertsen July 16, 1935 2,398,556 Pearson Apr. 16, 1946 2,456,061 Hohwart Dec. 14, 1948 2,479,898 Beaudette Aug. 23, 1949 FOREIGN PATENTS 470,256 Germany Jan. 9, 1929 

